This invention relates in general to color reproducing cathode ray tubes and in particular to a face panel arrangement for use in such tubes.
The conventional mass produced color picture tube employed in most present day color television receivers comprises a glass funnel, having a neck portion which houses electron beam generators, and a glass face panel comprising a curved target surface upon which a luminescent screen formed of a multitude of phosphor triads is deposited. In addition to the target surface the face panel comprises an integrally formed rearwardly extending flange that circumscribes the target surface. This flange is provided with three or more mounting studs that serve to support a color selection electrode, which usually takes the form of an aperture mask.
In order for the electron beams to achieve proper color selection the apertures in the mask must individually effect registration with assigned ones of the phosphor triads comprising the luminescent screen. Effecting and maintaining such registration in prior art picture tubes is achieved by resort to a massive, and thus costly, mounting arrangement for the aperture mask. To this end the mask is welded to a relatively heavy gauge steel frame which serves to support the mask as well as to impart rigidity to it. This frame is provided with three or more mounting clips each of which has one end secured to the frame while the other end is provided with an opening or other provision for engaging an assigned one of the studs affixed to the flange of the face panel. The above-described face panel and mask assembly, which comprises a unit of substantial mass, is then affixed to the funnel portion of the envelope by means of a frit seal.
In addition to the problems encountered in handling the frame and mask subassembly and, thereafter, the mask and face panel assembly, the use of a flanged face panel represents a significant cost. This obtains because of glass design considerations necessarily entailed, due to the flange, in producing a face panel having the requisite integrity. By the same token, the mask frame itself is also an item which contributes to the overall cost of the assembly.
The actual weight of the mask and its frame are also of consequence as respects another consideration, that is, the G forces to which a color picture tube is unavoidably subjected. More particularly, when a picture tube is jarred or vibrated the G forces which the mask and frame subassembly apply to the mounting studs affixed to the face panel flange are considerable in view of the weight of the frame. When these forces are substantial they can cause deformation of the frame and/or the mounting clips which, in turn, effect a misregistration between the apertures of the mask and their assigned phosphor triads. In some instances the G forces to which the tube is subjected may be sufficient to cause the shadow mask and its frame to fracture or even dislodge one of the mounting studs on the flange of the face panel.
In view of the foregoing, it is apparent that a reduction in the overall weight of the aperture mask mounting frame, as well as the face panel, is most desirable. While efforts have been expended to achieve a lighter weight mask-frame subassembly, the results, for the most part, simply amounted to a reduction in the mass of the mounting frame. While this approach has produced a lighter mask subassembly, the improvement is substantially one of degree only and has not been accompanied by any significant improvement in the mask mounting arrangement or in the overall cost of a face panel assembly.
It is therefore an object of the invention to provide a face panel assembly for use in a color picture tube which represents an improvement over prior art face panel assemblies by its compactness, low mass, economy of manufacture, and simplicity and by its use of a color selection electrode which has low mass and a capability of conforming to its supporting faceplate.
______________________________________ State of the Art: ______________________________________ 2,222,197 2,906,904 3,350,593 3,548,235 British 2,562,163 2,916,644 3,358,170 3,601,650 1,278,633 2,733,366 2,922,063 3,404,302 3,639,799 1,278,634 2,824,990 2,961,560 3,529,199 3,700,949 1,278,635 3,735,179 ______________________________________